Dual‐Molecule Systems for NIR‐II Fluorescence Imaging and Regulated Phototherapy

ABSTRACT Based on the characteristics of aggregation‐induced emission (AIE) and aggregation‐caused quenching (ACQ), this work constructed six distinct AIE&ACQ bimolecular systems (including D‐A and A‐D types) through the noncovalent combination of tetraphenylethylene (TPE) and boron‐dipyrromethene (BODIPY) dyes. This strategy avoids complex synthetic steps through a simple mixing process and enables flexible modulation of optical properties via intermolecular interactions, with their regulatory capability exceeding the traditional heavy‐atom effect and conjugation effect in single‐molecule systems. Experiments show that the fluorescence emission of A‐D type bimolecular systems in solution exhibits a significant redshift to 900–950 nm, reaching the NIR‐II window; after nanoparticle encapsulating, the redshift is somewhat reduced but still retains distinct NIR‐II characteristics. The photothermal and photodynamic properties of the systems can be directionally tuned by molecular pairing. Theoretical calculations confirm that intermolecular interactions significantly reduce Δ E st , enhance spin–orbit coupling and K ISC , thereby cooperatively promoting reactive oxygen species generation and non‐radiative relaxation. The bimolecular system nanoparticles demonstrate mild photothermal (PTT) and excellent photodynamic (PDT) synergistic capabilities with deeper tissue penetration in a CT26 tumor‐bearing mouse model, exhibiting efficient tumor targeting, prolonged retention, and significant phototherapeutic efficacy. This study provides a novel strategy for flexibly regulating NIR‐II fluorescence and PDT/PTT synergistic performance through intermolecular interactions.